Academic articles on such subjects can be pretty dull, but this one is fun.

Tom E. Sullenberger, "Ajax Meets the Jolly Green Giant," Jour. American Folklore, 1974, vol. 87, no, 343, pp. 53-65.

The Chicago-based agency that handles the Green Giant campaign, drew this comment from J. D. Femina, a competitor:

"Burnet is the agency that figured out a way to sell vegetables: they invented this green eunuch called the Jolly Green Giant. The giant stands for good quality, and he comes from the Valley of the Jolly Green Giant and the people look at this big green guy and figure, "Gee, it's got to be good stuff." And they Buy. Who knows what the Green Giant stands for? Maybe because he's so big he means quality... That big green son of a bitch, the Jolly Green Giant, is fantastic. He sells beans, corn, peas, everything. When you watch the Jolly Green Giant, you know it's fantasy and yet you buy the product. Do you know what other food advertising is? Most food advertising is like gone by the boards, you don't even see it. But the Jolly Green Giant, it's been automatic success when he's on that screen."

Whether "there exists a more than coincidental similarity between the Jolly Green Giant and the fertility figures compiled by Frazier* is a tempting conjecture, but what or how much to make of this apparent similarity is a knotty issue indeed."
*"The Golden Bough."

....."The related question of whether the Jolly Green Giant was knowingly produced by people who consciously set about to revive a latter day spirit of vegetation with friends and relatives back in the old country, whether he was born from the collective unconcious of the parties involved, or whether he was merely the accidental offspring of an agency "skull session" also invite imaginative surmise."